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Thread: Personal EV journey.
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19th July 2023, 06:29 PM #106New Member
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There is a certain irony that ICE vehicles seem to be affected less by towing additional loads. The on-road energy conversion efficiency of the ICE engine in a vehicle is of the order for 15 to 20%, compared to a ~30% theoretical limit for the same ICE engine at perfect load and rpm settings. The irony part is that the additional load on the engine causes the driver to exert more pressure on the accelerator, which in turn increases the engine's load ratio, and consequently the energy conversion efficiency closer to the theoretical limit for the engine's compression ratio. This masks some of the fuel consumption effect of the extra energy needed to pull the additional load.
In the case of a BEV the additional energy used for the trailer accelerating and going up hills is offset by additional energy recovered on deceleration and descending hills, but the extra energy to pull additional load is not offset by an increase in engine efficiency that happens in an ICE. The BEV's on road energy conversion efficiency (~100% thanks to regenerative braking) will be hardly affected by the load on the motor - it remains close to 100%. Regardless more work needs to be down to move more weight. Try a pushing a full wheelbarrow compared to an empty one, and it's nothing to do with aerodynamics. At suburban speeds aerodynamics can pretty much be disregarded, because aerodynamic losses go up at >cube of the airspeed.
On my Nissan Leaf because of the losses in the many processes involved in regeneration (a varying % is lost in: battery conversion efficiency / motor controller efficiency / motor efficiency / transmission losses, tyre losses, etc on acceleration, then all those processes in the reverse order on regeneration) the round cycle efficiency of regeneration is only about 50%. This is one area where improvements in design leading to better range can be expected.
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20th July 2023, 10:49 AM #107.
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The space saver are tyre has arrived.
The seriously solid alloy wheel is much sturdier than all other space saver wheels I've seen and the tool kit appear to be very good quality, but at the price paid I would expect nothing less,
The wheel also comes in a sturdy rip stop nylon bag with decent handles which makes it easier to carry.
There is supposed to be a way to store the wheel in the Large storage space under the rear cargo compartment floor but haven't worked out how to do this yet.
The space under the floor of the rear cargo compartment is also required to store changing cables and the tools so I'm not going to place the wheel in the vehicle except when I leave town.
TeslaSpaceSave.jpg
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20th July 2023, 12:18 PM #108
Bob - at least you have the option ! I know many BYD owners in rural areas aren't happy with the "Goo+Pump" repair kit that comes with the Atto 3, and BYD don't offer any factory solution for a proper space-saver spare. Then some resourceful Atto 3 owner somewhere discovered that the space-saver spare for the Toyota Rav 4 was a perfect fit in terms of wheel size and fixing pattern, so these have been in high demand ever since.....
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20th July 2023, 09:44 PM #109
question for "BobL" and "Mr Bush"
If Teslas, Atto 3s, BYDs are supplied -- in standard configuration -- without a spare tyre, are the vehicles fitted with Run Flat tyres?
As far as I know, those BMWs that do not come with a light weight spare are fitted with run flats as standard.
I understand that Tesla's -- at least in the US and Canada -- come with full roadside assist, meaning that Tesla will dispatch a spare tyre or flat top tow truck to wherever the vehicle has suffered a flat and carry the vehicle to where a spare can be fitted.
Is the same true in Australia?regards from Alberta, Canada
ian
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20th July 2023, 10:16 PM #110
All BYD Atto 3s in Australia are NOT supplied with run flat tyres. In fact, they are supplied with a spectacularly cheap and crappy normal tyres (Batman brand) which offer such poor grip that several owners have changed them out for a better tyre even from new (before they wore out). EVs generate massive torque from standstill, Atto 3 is front wheel drive, so tyre quality does matter. The car is supplied with a repair kit containing a sealant goo plus a compressor to re-inflate the tyre. Of course, this generally only works for small punctures , so if you damage the tyre sidewall you will be left relying on roadside assist. Hence some more creative owners, travelling off the beaten track, finding their own space-saver spare from Toyota Rav 4. To be fair, Atto 3 fits into that increasingly popular category of car which looks like an SUV, but should never actually venture off sealed roads......
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20th July 2023, 10:40 PM #111
Bob,
did you manage any recharge at the Wyalkatchem Men's Shed? or did you do the out and back trip without a recharge?
my concern regarding your "rubber band" tyres is not their width 275mm(?), but their low (35%) profile. At a profile of 35% there's not a lot of air between any pothole and the tyre's rim.
The 19in, 245/45 tyres fitted to my X3 perform similarly. As a general rule, I don't need to slow (from 100 km/h) for any corner posted with an advisory speed of 75 km/h or greater.
I would expect your 275/35 to have even better grip.
you do know that "advisory speeds" are based on driver comfort and not a vehicle's road holding ability?
The tool used is a "ball bank indicator" that measures centripetal (sideways) acceleration of the vehicle -- which roughly translates to how far a diver will slide sideways on a bench seat.
are you really sure that the road noise is associated with the "big tyres".
My experience driving around 70,000 km / year (in Canada) -- using summer and winter tyres -- is that a tyre's tread pattern is the overwhelming factor affecting road noise heard inside the vehicle cabin. Neither width -- my summers are on 19/245 rims, the winters on 18/235 rims -- nor profile has any noticeable effect.
what vehicle were you using for your country driving before you bought the Tesla?
Your new Tesla might be a bit heavier, but its aero shape should make a huge difference in how the vehicle handles buffeting from oncoming traffic.regards from Alberta, Canada
ian
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21st July 2023, 09:13 AM #112.
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I did some charging at the Wyalkatchem shed, starting out with 98% of battery - added 12% at the Wyalkatchem shed (It turned out they did not have 3P but did have a 15A socket) and arrived home with 14%. According to my my brother when the battery says zero you have about 50km left but I did not wish to confirm this.
The vehicles we've towed trailers and camper vans with in the past have been, a Mitsubishi Van, Mitsubishi Veradas, various Subaru Foresters (petrol and diesel versions), HiAce van (I still have this vehicle) and recently an Isuzu MUX (Amanda's last vehicle).
However the Tesla went around corners I felt way safer than any of our previous vehicles although the Subarus were also pretty good at cornering. The only comparable vehicle I owned that came close to the Tesla at cornering was my Alfa GTV that I had in the 1970's, and various Alfa/Lancia/Fiats hired in Europe.
Road noise. I agree the tread pattern is a component, but whatever the causes the more tread pattern in contact there is with the road the greater the noise.
The 'Zero P40" Pirelli tyres on the Tesla are touted as low noise tread pattern tyres so there must have been other factors involved
In a 2013 study undertaken by a team of Austrian Engineers on the causes of tyre/road noise the following noise contributions were determined.
see https://ris.utwente.nl/ws/files/5465799/Bekke06.pdf
Unfortunately tyre width was not tested presumable because it would be linear with width.
Screenshot 2023-07-21 at 5.48.56 am.png
Tyre road noise is a big issue but the tyre itself is a minority component because the road itself (roughness and sound absorption) contribute most of the noise,
Tread pattern only contributes ~10%.
On reflection I remember the effect of road roughness was quite marked because some sections of (smoother) bitumen were much quieter than others.
I'm taking 2 sisters to Busselton today (436km round trip) where they have a 50kW charger next to the pub we're having lunch in with relatives that live down that way.
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21st July 2023, 10:28 PM #113.
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The trip to Busselton went very smoothy. All up 456 km at 173 W/km, not that different to the Wyalkatchem trip @ 176 W/km..
Some light showers but great road and time went very quickly with two sisters nattering all the way on all sorts of topics.
The main difference between this and the Wyalkatchem trip was that the Busselton trip was done at higher speeds, fewer hills and much fewer bends ..
Traffic was light so managed to sit on 111 km/hr for the much of the way.
Recharging to 80% at the 50kW charger in front of the Busselton jetty was done in quicker than the time taken to have lunch.
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21st July 2023, 11:36 PM #114
BobL, I'd bet the cabin noise is non-existent without the engine revving and roaring
Must be nice.
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22nd July 2023, 09:27 AM #115.
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Unfortunately this is not always so - as I mention above, at speed (ie above 90 kph) the tyre-road noise on some rough surfaces becomes noticeable and I find it annoying because it is so quiet at lower speeds eg at 60kph or on smooth surfaces. . It is especially noticeable at 110 when the bitumen changes from rough to smooth and back again.
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22nd July 2023, 01:37 PM #116.
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I have an 7.9m long, single width car, carport, that I was hoping to fit my 5x8, long drawbar trailer (4.04m total length) and new vehicle (4.75m) completely under.
As you can see the combined lengths are 890 mm too long.
Trailer1.jpg
I was hoping the car's rear underside would be high enough so I could back over the trailer coupling but alas all that gets me is about 250mm before it makes contact with the underside of the vehicle.
I invited my brother in law around for coffee and to look at possible solutions and he suggested,
- standing the trailer up on its backside with a winch, but it's too tall for the available carport roof height (3.6m).
- hinging the drawbar so it would fold up - ie a lot of work. As a highly skilled metal fabricator and welder, I have no doubt he would do an great job but then it should probably go over the MVD pits etc
Finally he said - "What's under the paving?". and I said an old red concrete drive way, so he suggested removing a few bricks so the drawbar would nestle below the level of the bricks like this.
Trailerposn5.jpg
Vehicle can now be backed all the way in.
Trailerposn2.jpg
The coupling handle clears the underside of the car by about 10 mm
Trailerposn4.jpg
I can back it in further than this but this about as far as I want to go, so as to leave enough room so that the vehcile rear hatch can be opened to let the dogs in and out.
Trailerposn1.jpg
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23rd July 2023, 09:45 AM #117
Bob
Is that lateral thinking or vertical thinking? Either way, a good outcome at zero cost.
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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23rd July 2023, 10:52 AM #118
Definitely "A Cunning Plan"
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23rd July 2023, 11:49 AM #119
Some interesting comments from an Atto 3 owner on one of the (many) BYD facebook forums, re. trailer towing. He found a big increase in power consumed just while towing an empty and fairly lightweight trailer due to increased wind resistance, and the power used didn't go up by much more even with the trailer loaded. Obviously this would vary depending on the terrain, e.g. hauling a heavy trailer mostly uphill, but on the flat wind resistance seems to dominate.
The religious theory of "Intelligent Design" is all very well, but why did God give the tortoise a drag coefficient of 0.01? #crappy_engineering
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24th July 2023, 09:11 AM #120.
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